Power wrenches for threaded members such as nuts and bolts are described in U.S. Pat. Nos. 3,706,244 and 2,972,918. The patented tools are especially adapted for flanges whose threaded connectors are arranged in a circular pattern. There is a need for power wrenches which are readily adaptable for use on connectors arranged in a straight line or in non-circular patterns. The power wrench actuator is usually a fluid-operated cylinder having a rod which engages the wrench arm at a substantially right angle. By limiting the rotation of the wrench arm to a small angle in response to a full stroke of the push rod, and by making the right angle to become established at the push rod's mid-stroke, the torque can be fairly accurately measured by measuring only the applied pressure in the cylinder.
When a tool is designed for a specific connector pattern, the desired right angle can be built into the tool. However, any subsequent adjustments, which may be required to position the tool's reaction members, will most likely change this right angle by an angular amount which is not easy to measure.
The consequences of working with an angle which varies from a right angle are twofold; maximum torque is not obtained per unit of pressure applied to the hydraulic cylinder, and torque measurements cannot be sufficiently accurately made by simply measuring the pressure in the fluid-operated cylinder. There is therefore a need for power wrenches which allow adjustments to the positions of their reaction members without disturbing the desired right angle relationship between the push rod and the wrench arm.
The above-mentioned patented tools produce reaction stresses, which are absorbed by the structures supporting the reaction members. There is a need for power wrenches which can internally absorb most of their self-generated reaction stresses.
Accordingly, it is a broad object of the present invention to provide new and improved power wrenches which are versatile, which easily adapt themselves for use on irregular connector patterns, which internally absorb most of the reaction stresses, which have a built-in right angle relationship that is not disturbed when making reaction set-up adjustments, and which can rotate members such as threaded connectors, the access to which is partially obstructed.